The invention is related to the field of injection molding plastic material articles.
More specifically, the invention is related to a plastic material injection molding machine comprising a mold having at least two mold portions and a handling system adapted to be inserted between the mold portions when the mold is in its open position, for transferring an article between the handling system and a predetermined mold portion, the handling system, moreover, comprising a transfer plate supported loosely therein, the handling system, further, being adapted to approach the predetermined mold portion such that prior to the transfer of the article a first reference means on the predetermined mold portion can be brought into a registering position with a second reference means on the transfer plate.
The invention is, further, related to a handling system having means for transferring an article between a handling system and a predetermined position, the handling system comprising a transfer plate supported loosely therein and being adapted to approach the predetermined position such that prior to the transfer of the article a first reference means on the predetermined position can be brought into a registering position with a second reference means on the transfer plate.
The invention, moreover, is related to a method for transferring an article between a handling system and a predetermined mold portion of a plastic material injection molding machine having a mold with at least two mold portions, the handling system being adapted to be inserted between the mold portions when the mold is in its open position, the handling system, moreover, comprising a transfer plate supported loosely therein, the handling system, further, being adapted to approach the predetermined mold portion such that prior to the transfer of the article a first reference means on the predetermined mold portion can be brought into a registering position with a second reference means on the transfer plate.
Finally, the invention is related to a method for transferring an article between a handling system and a predetermined position, the handling system comprising a transfer plate supported loosely therein, the handling system, further, being adapted to approach the predetermined position such that prior to the transfer of the article a first reference means on the predetermined position can be brought into a registering position with a second reference means on the transfer plate.
A plastic material injection molding machine, a handling system as well as methods of the types specified before are known in the art.
In connection with the plastic material injection molding machines, so-called handling systems are used which, when the mold is open, are inserted between the mold portions which are then at a distance from each other, for executing various objectives.
The most important objective of a handling system is to pick up the finished injection-molded plastic material articles from the hollow cavities of the mold after the opening of the mold, when the plastic material articles are ejected from the hollow cavities by means of ejector pins. For that purpose the handling systems are provided with an arm adapted to be inserted between the mold portions, the arm being equipped with corresponding receiving means. The receiving means may be configured mechanically, pneumatically or otherwise.
These configurations are basically independent of how the mold of the injection molding machine is configured in detail, i.e. whether the mold consists only of two mold portions or whether the mold is configured as a so-called stack mold comprising a center platen and laterally adjoining mold portions. For these various applications the handling system needs only to be configured correspondingly by multiplication or otherwise.
A further objectives of handling systems consists to insert certain parts into the hollow cavities of the mold prior to the beginning of the injection cycle. These parts or devices are subsequently immersed in liquid plastic material when the mold is closed so that the finished plastic material articles are provided with inserts embedded therein.
Such inserts may be so-called xe2x80x9clabelsxe2x80x9d as are utilized as cover surfaces for smart cards or the like. Inserts, however, may also be electrical connector elements, i.e. contact pins or the like, as an example being embedded into a socket of an electrical component during the injection process. Moreover, such inserts may be reinforcing devices, hinges, mechanical fasteners or the like. Insofar, the invention is in now way restricted.
With all these objectives of handling systems a basic problem exists in that during the insertion of the handling system or of the handling system arm, respectively, between the mold portions a coordination in position between the handling system or the arm, respectively, on the one hand and that predetermined mold portion on the other hand must be established that shall be approached by the handling system. Considering that handling systems, in particular as used in connection with highly complex injection molding machines with corresponding external dimensions have correspondingly long cantilevered arms, it is not always possible to achieve a precise coordination of the movements even if precise position drives are utilized.
The afore-mentioned problems also arise outside of the mold when the handling system with its arm is displaced into a position outside the plastic material injection molding machine. At this external position, for example, those finished injection-molded plastic material articles that had been unloaded from the mold before, are transferred to further stations or, in the case of inserting parts, these inserts are picked up at those external positions for being subsequently transferred into the hollow cavities of the mold. In any event, it is necessary to approach that position outside of the mold exactly when it is in a station outside of the machine. However, even there is no such station outside of the machine, a precise positioning is also mandatory because a precise initial position for the arm of the handling system must be established in order to enable a precise displacement towards its end position between the mold portions.
The afore-discussed problems are also of importance for handling systems as used in general applications, i.e. as are used outside the field of plastic material injection molding machines. The invention is, hence, not limited to this particular application but is related to all conceivable applications of handling systems irrespective of the particular technical field.
It is known in the art to provide the predetermined mold portion on the one hand and its opposed side of the handling system on the other hand with a reference means or mark which have to be brought into engagement with one another in order to ensure that during the transfer of the article an exact relative positioning between the handling system and the mold portion prevails. This, too, is independent of whether the term xe2x80x9ctransfer of the articlexe2x80x9d is to be understood to mean the un-loading of a finished injection-molded plastic material article or the deposition of an insert or the like.
In the simplest case the reference means on the mold portion on the one hand and on the handling system on the other hand are complementary mechanical elements, for example a bore and a pin. Preferably, the bore is provided with a canted or beveled insertion surface and the pin is pointed at its front tip. When the handling system is inserted between the mold portions in a radial direction (relative to the axis of the injection molding machine) and then approaches the predetermined mold portion in an axial direction and, further, when the reference means are not exactly flush with one another, the afore-mentioned canted or beveled insertion surface of the bore or the also above-mentioned pointing of the pin effects that the pin will be inserted into the bore even if there is a certain offset between the two.
However, one will easily appreciate that such a correction movement within a radial plane will effect a mechanical constraint within the handling system because the handling system is forced to move out of the nominal position that it had just attained.
It is, therefore, also known in the art to provide a separate transfer plate for the transfer of the article within the handling system or within the inserted arm of the handling system and to support the transfer plate loosely, for example elastically movable within that radial plane, in the handling system or its arm.
Accordingly, during a correction movement out of the attained nominal position in the meaning of what was discussed above, only the transfer plate is slightly shifted within the range of movement of its movable support whereas no mechanical constraint is exerted on the handling system.
However, this prior art handling system has the disadvantage that the movable support of the transfer plate within the handling system causes problems during a fast displacement of the handling system, in particular when the handling system is strongly accelerated or strongly decelerated. The movably supported transfer plate with its movable support will hit against its mechanical stop in these cases, wherein this will happen several times during a handling process, namely during each acceleration and each deceleration. One has to bear in mind insofar that in the interest of a minimum cycle time of the plastic material injection molding machine, it is desired to move the handling system as quickly as possible, i.e. with the highest possible accelerations and decelerations.
The uncontrolled oscillatory movement of the transfer plate within the handling system will not become apparent only acoustically but will result in a significant wear of the elastic support and, hence, in its breakdown within a very short period of time. This, again, results in downtimes of the plastic material injection molding machine so that the resulting productivity of the plastic material injection molding machine may get lost entirely or partially in spite of minimum cycle times.
It is, therefore, an object underlying the invention to provide a plastic material injection molding machine as well as a method of the kind specified at the outset such that the above-discussed disadvantages are avoided.
In particular, it shall become possible to make a correction in position also in a wrong positioning of the transfer plate when it has attained its nominal position without substantial mechanical reactions on the handling system. Moreover, this shall become possible without the need of limiting the velocity of displacement, in particular the accelerations and the decelerations of the handling system.
In a plastic material injection molding machine of the type specified at the outset, this object is achieved according to the invention in that a clutch is provided for bridging the loose support.
In a handling system specified at the outset, the object is achieved according to the invention in that a clutch is provided for bridging the loose support.
According to the first method mentioned at the outset, the object is achieved according to the invention in that the loose support is bridged by means of a clutch at least during the insertion of the handling system between the mold portions.
Finally, according to the second method specified at the out-set, the object is achieved according to the invention in that the loose support is bridged by means of a clutch at least before the approachment to the predetermined position.
The object underlying the invention is thus entirely solved.
If the movable support of the transfer plate is blocked at any time when it is not needed during the bringing into engagement of the reference means, one has no limiting side conditions with respect to the velocity, acceleration or deceleration of displacement. Instead, the handling system may be displaced with the maximum velocity, acceleration and deceleration as is possible for the particular design of the handling system with-out any influence on the mechanical stability of the transfer plate which is mechanically locked to the handling system during these movements because the clutch is closed.
The invention, therefore, has significant advantages in particular when large transfer plates are required as is the case for multiple tools having a very large number of hollow cavities for the simultaneous manufacture of a plurality of typically small plastic material articles. Such large transfer plates have correspondingly large masses. Also in such applications the invention allows to operate with very quick movements.
In a preferred embodiment of the invention, the movable support is configured by an elastic support.
This measure has the advantage that the movable transfer plate after having effected an elastic movement, will automatically return essentially into the same initial position so that no large corrections in movement are necessary, however, it is also possible to configure the support plastically or braked or otherwise.
In a preferred embodiment of the inventive injection molding machine, the transfer plate is supported in an arm of the handling system.
This measure, known per se, has the advantage that only a narrow arm has to be inserted between the mold portions so that the mold portions need only to be opened by a relatively small amount. However, according to the invention it is also possible to configure the transfer plate as the arm of the handling system as a whole, i.e. to support the entire arm movably within the handling system, for example elastically or otherwise.
In another preferred embodiment of the inventive machine, the predetermined mold portion has an open surface when the mold is in its open position, the transfer plate being supported to move elastically within the plane defined by the open surface.
This measure has the advantage that the transfer plate is not only supported elastically along an axis but along a plane instead defined by two axes, and may correspondingly be latched by means of the clutch so that also complex motional sequences may be effected while entering or leaving a particular position.
In another embodiment of the inventive machine and the inventive method the clutch is adapted to be opened overlapping in time with the bringing into a registering position of the reference means and to be closed overlapping in time with the bringing out of a registering position of the reference means.
This measure has the advantage that the mechanical latching or locking of the transfer plate may be transferred automatically from the handling system or its arm to the predetermined mold portion so that the transfer of the article between the mold portion and the transfer plate may be effected while these elements are precisely aligned relative to one another. This enhances, for example, the precision of embedded contact elements of electrical components being an essential quality feature of such components.
Moreover, these measures have the advantage that the elastic support of the transfer plate is set free effectively for the absolute minimum in time, i.e. the transfer step for the article between the predetermined mold portion and the transfer plate, while otherwise the transfer plate is mechanically latched on the handling system or its arm at any time.
Correspondingly, for another variation of the inventive machine and the inventive method, respectively, the clutch is adapted to be opened automatically when the handling system approaches the predetermined mold portion.
This measure has the further essential advantage that a separate control for the clutch is not necessary at all because the corresponding clutch elements are actuated by the approaching movement itself so that the opening process and the subsequent closing process of the clutch is effected in an optimum way without the necessity of a complicated control.
In a mechanical embodiment of this variation, the clutch is adapted to be actuated by means of a rod being axially dis-placeable relative to the transfer plate in the direction of approachment of the handling system towards the predetermined mold portion, the rod protruding from a surface of the transfer plate opposite the predetermined mold portion.
This measure has the advantage that the clutch is actuated in a very simple manner by actuating the corresponding elements during the approachment of the handling system by making mechanical contact.
According to an improvement of this embodiment, the rod has a front side being flush with the second reference means as viewed in the direction of approachment.
This measure has the advantage specified above that the bringing into engagement of the reference means on the one hand and the actuation of the clutch on the other hand are effected synchronously as is also the case for the corresponding opening process.
In this respect it is preferred when the rod is journalled within the arm to be displaced in a longitudinal direction, that the clutch is configured by a section of the rod and by a seat surface in the transfer plate associated to the rod section, the clutch immobilizing the rod section on the seat surface in a plane transversal to the direction of approachment when the rod is in a first operational axial position and letting the rod section move freely when the rod is in a second operational axial position.
This measure has the advantage that the clutch is configured mechanically in an extremely simple manner in that only a rod is shifted to and fro in an axial direction between two operational positions.
This holds true in particular if, according to another improvement of this variation, the rod section and the seat surface are configured as complementary cones.
This measure has the advantage that when the cones adjoin each other, a reliable mechanical lock is guaranteed within the plane whereas on the other hand when the cones are axially off-set from one another, a sufficient clearance is guaranteed along the two axes defining the plane.
In this regard it is further preferred when the rod is held in the first operational axial position under the action of a spring, the spring being compressed during the transition from the first to the second operational axial position.
This measure has the advantage that during the entire movement of the handling system into and out of the gap between the mold portions, the spring holds the clutch in its closed state so that the transfer plate is mechanically latched to the handling system or its arm, respectively. Only during the short period of time of transfer to the predetermined mold portion, the spring is compressed and the clutch is thereby opened, which, again, activates the elastic support of the transfer plate.
Moreover, the machine according to the invention is preferred when the transfer plate is fixed to the handling system in the direction of approachment of the handling system towards the predetermined mold portion.
This measure has the advantage that clutches of simple design may be operated by axially displacing the handling system, as well already explained in connection with the above-mentioned embodiments. A relative movement between the transfer plate and the handling system must be only be guaranteed within the plane.
In this connection, a design is preferred according to which the transfer plate is surrounded by a flange of the handling system in the direction of approachment.
This measure has the advantage that the afore-mentioned axial fixation may be achieved in a particular simple manner.
According to embodiments of the inventive machine, reference means are preferred which, when brought into the registering position, come to engage one another in a form-fitting relationship. This may be effected, as known per se, in that the reference means are configured as a bore, in particular a blind bore, and as a pin, respectively, as is known in the art and as has already been discussed above.
As already mentioned, the invention is not restricted to the application in plastic material injection molding machines. All of the afore-mentioned examples and advantages hold likewise true for general applications of handling systems as well as for the indicated methods for transferring an article.
Further advantages will become apparent from the description and the enclosed drawing.
It goes without saying that the afore-mentioned features and those that will be explained here and after may not only be used in the particularly given combination, but also in other combinations or alone without leaving the scope of the present invention.